Shutter member, a lithographic apparatus and device manufacturing method

ABSTRACT

An immersion lithographic apparatus that includes a substrate table, a fluid handling structure and a swap table. The substrate table is configured to support a substrate. The fluid handling structure is configured to supply and confine immersion liquid to a space defined between a projection system and the substrate table, the substrate, or both. The swap table has a shutter surface configured to be under the fluid handling structure during, for example, swap of the substrate on the substrate table. In use, a transfer surface between a surface of the substrate table and a surface of the swap table is moved under the fluid handling structure to help stop escaping immersion liquid. A shutter member and a method are also disclosed.

This application claims priority and benefit under 35 U.S.C. §119(e) toU.S. Provisional Patent Application No. 61/241,724, entitled “A ShutterMember, A Lithographic Apparatus and Device Manufacturing Method”, filedon Sep. 11, 2009. The content of that application is incorporated hereinin its entirety by reference.

FIELD

The present invention relates to a shutter member, a lithographicapparatus and a device manufacturing method.

BACKGROUND

A lithographic apparatus is a machine that applies a desired patternonto a substrate, usually onto a target portion of the substrate. Alithographic apparatus can be used, for example, in the manufacture of,for example, an integrated circuit (IC), a device or an IC device. Inthat instance, a patterning device, which is alternatively referred toas a mask or a reticle, may be used to generate a circuit pattern to beformed on an individual layer of the IC, device or IC device. Thispattern can be transferred onto a target portion (e.g. comprising partof, one, or several dies) on a substrate (e.g. a silicon wafer).Transfer of the pattern is typically via imaging onto a layer ofradiation-sensitive material (resist) provided on the substrate. Ingeneral, a single substrate will contain a network of adjacent targetportions that are successively patterned. Known lithographic apparatusinclude so-called steppers, in which each target portion is irradiatedby exposing an entire pattern onto the target portion at one time, andso-called scanners, in which each target portion is irradiated byscanning the pattern through a radiation beam in a given direction (the“scanning”-direction) while synchronously scanning the substrateparallel or anti-parallel to this direction. It is also possible totransfer the pattern from the patterning device to the substrate byimprinting the pattern onto the substrate.

It has been proposed to immerse the substrate in the lithographicprojection apparatus in a liquid having a relatively high refractiveindex, e.g. water, so as to fill a space between the final element ofthe projection system and the substrate. In an embodiment, the liquid isdistilled water, although another liquid can be used. An embodiment ofthe present invention will be described with reference to liquid.However, another fluid may be suitable, particularly a wetting fluid, anincompressible fluid and/or a fluid with higher refractive index thanair, desirably a higher refractive index than water. Fluids excludinggases are particularly desirable. The point of this is to enable imagingof smaller features since the exposure radiation will have a shorterwavelength in the liquid. (The effect of the liquid may also be regardedas increasing the effective numerical aperture (NA) of the system andalso increasing the depth of focus.) Other immersion liquids have beenproposed, including water with solid particles (e.g. quartz) suspendedtherein, or a liquid with a nano-particle suspension (e.g. particleswith a maximum dimension of up to 10 nm). The suspended particles may ormay not have a similar or the same refractive index as the liquid inwhich they are suspended. Other liquids which may be suitable include ahydrocarbon, such as an aromatic, a fluorohydrocarbon, and/or an aqueoussolution.

Submersing the substrate or substrate and substrate table in a bath ofliquid (see, for example, U.S. Pat. No. 4,509,852) is a form ofimmersion system arrangement. The arrangement requires that a large bodyof liquid should be accelerated during a scanning exposure. This mayrequire additional or more powerful motors and turbulence in the liquidmay lead to undesirable and unpredictable effects.

Another arrangement proposed is for a liquid supply system to provideliquid on only a localized area of the substrate and in between thefinal element of the projection system and the substrate using a liquidconfinement system (the substrate generally has a larger surface areathan the final element of the projection system). One way which has beenproposed to arrange for this is disclosed in PCT patent applicationpublication no. WO 99/49504. This type of arrangement may be referred toas a localized immersion system arrangement.

Another arrangement is an all wet arrangement in which the immersionliquid is unconfined as disclosed in PCT patent application publicationWO 2005/064405. In such a system, the immersion liquid is unconfined.The whole top surface of the substrate is covered in liquid. This may beadvantageous because then the whole top surface of the substrate isexposed to the substantially same conditions. This may have an advantagefor temperature control and processing of the substrate. In WO2005/064405, a liquid supply system provides liquid to the gap betweenthe final element of the projection system and the substrate. Thatliquid is allowed to leak over the remainder of the substrate. A barrierat the edge of a substrate table prevents the liquid from escaping sothat it can be removed from the top surface of the substrate table in acontrolled way. Although such a system improves temperature control andprocessing of the substrate, evaporation of the immersion liquid maystill occur. One way of helping to alleviate that problem is describedin United States patent application publication no. US 2006/0119809. Amember is provided which covers the substrate W in all positions andwhich is arranged to have immersion liquid extending between it and thetop surface of the substrate and/or substrate table which holds thesubstrate.

In European patent application publication no. EP 1420300 and UnitedStates patent application publication no. US 2004-0136494, each herebyincorporated in their entirety by reference, the idea of a twin or dualstage immersion lithography apparatus is disclosed. Such an apparatus isprovided with two tables for supporting a substrate. Levelingmeasurements are carried out with a table at a first position, withoutimmersion liquid, and exposure is carried out with a table at a secondposition, where immersion liquid is present. Alternatively, theapparatus has only one table.

After exposure of a substrate in an immersion lithographic apparatus,the substrate table is moved away from its exposure position to aposition in which the substrate may be removed and replaced by adifferent substrate. This is known as substrate swap. In a two stagelithographic apparatus, the swap of the tables may take place, forexample, under the projection system.

In an immersion apparatus, immersion liquid is handled by a fluidhandling system or apparatus. A fluid handling system may supplyimmersion fluid and therefore be a fluid supply system. A fluid handlingsystem may at least partly confine fluid and thereby be a fluidconfinement system. A fluid handling system may provide a barrier tofluid and thereby be a barrier member. Such a barrier member may be afluid confinement structure. A fluid handling system may create or use aflow of fluid (such as gas), for example to help in handling liquid,e.g. in controlling the flow and/or the position of the immersion fluid.The flow of gas may form a seal to confine the immersion fluid so thefluid handling structure may be referred to as a seal member; such aseal member may be a fluid confinement structure. Immersion liquid maybe used as the immersion fluid. In that case, the fluid handling systemmay be a liquid handling system. The fluid handling system may belocated between the projection system and the substrate table. Inreference to the aforementioned description, reference in this paragraphto a feature defined with respect to fluid may be understood to includea feature defined with respect to liquid.

SUMMARY

After exposure a substrate in a lithographic apparatus, the substrate isremoved from a substrate table on which it is supported and a newsubstrate is placed on the substrate table for exposure. This process isoften referred to as substrate swap. Immersion liquid during exposure isconfined in a space between a fluid handling structure, the projectionsystem and a facing surface of the substrate table, a substrate or both.It is desirable to retain immersion liquid in the space during, forexample, substrate swap. This may be achieved, for example, by havingthe fluid handling structure located over a shutter member (e.g., bymoving the shutter member to under the fluid handling structure). Insome designs of an immersion lithography system the shutter member maybe located beyond the outer edge of the substrate table, for example theshutter member may be another table (or swap table) or a retractablebridge between substrate table and the other table. The other table maybe another substrate table supporting a next substrate for exposure suchas in a dual stage lithographic apparatus, or a measurement table whichis designed so as not to support a substrate.

Located at the edge of the substrate table which during, for example,substrate swap moves out from under the fluid handling structure, theremay be components of a positioning system. For example, in or on thesurface of the substrate table near its edge may be a positioning plate,such as an encoder grid. The positioning plate is used to determine theposition of the substrate table, and therefore a substrate positioned onthe substrate, relative to one or more other components of thelithographic tool, such as the projection system.

As the substrate table, and the shutter member, move relative to thefluid handling structure there is a risk that immersion liquid will belost from the immersion space to the surface of the positioning plate.Immersion liquid on the positioning plate may interfere with thepositioning system and affect its accuracy.

It is desirable to alleviate the aforementioned problem or one or moreother problems, whether identified herein or elsewhere, by reducing, ifnot preventing, the risk of interference of immersion liquid with thepositioning system.

According to an aspect, there is provided an immersion lithographicapparatus comprising: a substrate table configured to support asubstrate; a fluid handling structure configured to supply and confineimmersion liquid to a space defined between a projection system and thesubstrate table, the substrate, or both; a swap table configured to belocated under the fluid handling structure to retain liquid in thespace; and a transfer surface configured to be located under the fluidhandling structure and between a surface of the substrate table and asurface of the swap table, wherein the transfer surface is configured toprevent immersion liquid moving over at least part of the transfersurface in a direction with a component perpendicular to a direction ofrelative motion between the fluid handling structure and the transfersurface.

According to an aspect, there is provided a shutter member for animmersion lithographic apparatus, the shutter member having at leastpart of a transfer surface configured to prevent immersion liquid in aconfined space moving over at least part of the transfer surface in adirection with a component perpendicular to a direction of relativemotion between the confined space and the shutter member.

According to an aspect, there is provided a device manufacturing method,the method comprising: confining immersion liquid in a space in contactwith a surface of a substrate table; replacing the surface of thesubstrate table with a shutter surface by moving the substrate table andthe shutter surface in one motion so that the substrate table moves awayfrom under the fluid handling structure and the shutter surface replacesthe surface of the substrate table under the fluid handling structure,wherein in replacing the substrate table with the shutter surface,moving a transfer surface under the fluid handling structure, thetransfer surface preventing immersion liquid moving over at least partof the transfer surface in a direction with a component perpendicular toa direction of motion of the transfer surface.

According to an aspect, there is provided a method of operating animmersion lithographic apparatus, the method comprising: supporting asubstrate on a substrate table; supplying and confining immersion liquidto a space defined by a fluid handling structure between a projectionsystem and the substrate table, the substrate, or both; replacing asurface of the substrate table under the fluid handling structure with ashutter surface, the shutter surface including a surface of a swaptable; moving a transfer surface under the fluid handling structure asthe surface of the swap table replaces the surface of the substratetable; and during moving the transfer surface, preventing immersionliquid moving over at least part of the transfer surface in a directionwith a component perpendicular to a direction of relative motion betweenthe fluid handling structure and the transfer surface.

According to an aspect, there is provided an immersion lithographicapparatus comprising: a substrate table configured to support asubstrate; a fluid handling structure configured to supply and confineimmersion liquid to a space defined between a projection system and thesubstrate table, the substrate, or both; a shutter member configured tobe located under the fluid handling structure during swap of thesubstrate on the substrate table, the shutter member being a swap table,wherein a transfer surface is arranged to be between surfaces of thesubstrate table and the swap table, the transfer surface configured tobe moved under the fluid handling structure and configured to preventimmersion liquid moving over at least part of the transfer surface in adirection with a component perpendicular to a direction of relativemotion between the fluid handling structure and the transfer surface.

According to an aspect, there is provided an immersion lithographicapparatus, comprising: a substrate table configured to support asubstrate; a fluid handling structure configured to supply and confineimmersion liquid to a space defined between a projection system and thesubstrate table, the substrate, or both; and a transfer surfaceconfigured to be located under the fluid handling structure and betweena surface of the substrate table and a shutter surface, the shuttersurface configured to replace the surface of the substrate table underthe fluid handling structure and the transfer surface configured toprevent immersion liquid moving over at least part of the transfersurface in a direction with a component perpendicular to a direction ofrelative motion between the fluid handling structure and the transfersurface.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1 depicts a lithographic apparatus according to an embodiment ofthe invention;

FIGS. 2 and 3 depict a liquid supply system for use in a lithographicprojection apparatus;

FIG. 4 depicts a further liquid supply system for use in a lithographicprojection apparatus;

FIG. 5 depicts a further liquid supply system for use in a lithographicprojection apparatus;

FIG. 6 depicts, in cross-section, a liquid confinement structure and afinal element of a projection system according to an embodiment of thepresent invention;

FIG. 7 depicts schematically, in plan, a dual stage arrangement with twosubstrate tables according to an embodiment of the invention;

FIG. 8 depicts schematically, in plan, a dual stage arrangement with twosubstrate tables according to an embodiment of the invention;

FIG. 9 depicts schematically, in plan, a dual stage arrangement with asubstrate table and a measurement table according to an embodiment ofthe invention;

FIG. 10 depicts schematically, in plan, a dual stage arrangement withtwo substrate tables according to an embodiment of the invention;

FIG. 11 depicts schematically, in plan, a dual stage arrangement withtwo substrate tables according to an embodiment of the invention;

FIG. 12 depicts schematically, in plan, a dual stage arrangement with asubstrate table and a measurement table according to an embodiment ofthe invention;

FIGS. 13, 14 and 15 depict schematically, in perspective, further detailof the three types of transfer lane depicted in FIGS. 7 to 12;

FIG. 16 depicts schematically, in plan, a transfer lane according to anembodiment of the invention;

FIG. 17 depicts schematically, in plan, a transfer lane according to anembodiment of the invention;

FIG. 18 depicts schematically, in plan, a transfer lane according to anembodiment of the invention;

FIG. 19 depicts schematically, in plan, a transfer lane according to anembodiment of the invention;

FIG. 20 depicts schematically, in plan, a substrate table according toan embodiment of the invention as shown in FIGS. 8, 9, 11 and 12;

FIG. 21 depicts schematically, in cross-section, an embodiment of thesubstrate table shown in FIG. 20 along the line X-X;

FIG. 22 depicts schematically, in cross-section, an embodiment of thesubstrate table shown in FIG. 20 along the line Y-Y;

FIG. 23 depicts schematically, in plan, a substrate table with anarrangement of sensor encoders;

FIG. 24 depicts schematically, in plan, an embodiment of the inventionhaving a substrate table with an arrangement of encoder sensors;

FIG. 25 depicts schematically, in cross-section, an embodiment of thesubstrate table shown in FIG. 20 along the line Y-Y;

FIG. 26 depicts schematically, in cross-section, an embodiment of thesubstrate table shown in FIG. 20 along the line X-X;

FIG. 27 depicts schematically, in cross-section, an embodiment of thesubstrate table shown in FIG. 20 along the line X-X;

FIG. 28 depicts schematically, in cross-section, an embodiment of thesubstrate table shown in FIG. 20 along the line Y-Y;

FIG. 29 depicts schematically, in perspective, the embodiment shown inFIGS. 25 and 26.

FIG. 30 schematically depicts, in perspective, a variation of theembodiment shown in FIG. 29;

FIG. 31 schematically depicts, in plan, an embodiment of a substratetable with a barrier around an inner edge of a grid;

FIG. 32 schematically depicts, in plan, an embodiment of a substratetable with a barrier around an outer edge of a grid;

FIG. 33 schematically depicts, in plan, an embodiment of a substratetable and a measurement table indicating a cleaning path over thesurfaces of both tables;

FIG. 34 schematically depicts, in plan, an embodiment of a dual tablearrangement with a substrate table and a measurement table having anextended surface to bridge the gap between the two tables;

FIG. 35 schematically depicts, in plan, an embodiment of a dual tablearrangement with two substrate tables, each table having an extendedsurface to bridge the gap between the two tables;

FIG. 36 schematically depicts, in cross-section, an embodiment of a dualtable arrangement with a substrate table and a measurement table asshown in FIG. 34;

FIG. 37 schematically depicts, in perspective, an embodiment of asubstrate table;

FIG. 38 schematically depicts, in cross-section, an embodiment of a dualtable arrangement with a substrate table of FIG. 37 and a measurementtable; and

FIG. 39 schematically depicts, in cross-section, detail of part of thedual table arrangement shown in FIG. 38.

DETAILED DESCRIPTION

FIG. 1 schematically depicts a lithographic apparatus according to oneembodiment of the invention. The apparatus comprises:

an illumination system (illuminator) IL configured to condition aradiation beam B (e.g. UV radiation or DUV radiation).

a support structure (e.g. a mask table) MT constructed to support apatterning device (e.g. a mask) MA and connected to a first positionerPM configured to accurately position the patterning device in accordancewith certain parameters;

a substrate table (e.g. a wafer table) WT constructed to hold asubstrate (e.g. a resist-coated wafer) W and connected to a secondpositioner PW configured to accurately position the substrate inaccordance with certain parameters; and

a projection system (e.g. a refractive projection lens system) PSconfigured to project a pattern imparted to the radiation beam B bypatterning device MA onto a target portion C (e.g. comprising one ormore dies) of the substrate W.

The illumination system may include various types of optical components,such as refractive, reflective, magnetic, electromagnetic, electrostaticor other types of optical components, or any combination thereof, fordirecting, shaping, or controlling radiation.

The support structure MT holds the patterning device. The supportstructure MT holds the patterning device in a manner that depends on theorientation of the patterning device, the design of the lithographicapparatus, and other conditions, such as for example whether or not thepatterning device is held in a vacuum environment. The support structureMT can use mechanical, vacuum, electrostatic or other clampingtechniques to hold the patterning device. The support structure MT maybe a frame or a table, for example, which may be fixed or movable asrequired. The support structure MT may ensure that the patterning deviceis at a desired position, for example with respect to the projectionsystem. Any use of the terms “reticle” or “mask” herein may beconsidered synonymous with the more general term “patterning device.”

The term “patterning device” used herein should be broadly interpretedas referring to any device that can be used to impart a radiation beamwith a pattern in its cross-section such as to create a pattern in atarget portion of the substrate. It should be noted that the patternimparted to the radiation beam may not exactly correspond to the desiredpattern in the target portion of the substrate, for example if thepattern includes phase-shifting features or so called assist features.Generally, the pattern imparted to the radiation beam will correspond toa particular functional layer in a device being created in the targetportion, such as an integrated circuit.

The patterning device may be transmissive or reflective. Examples ofpatterning devices include masks, programmable mirror arrays, andprogrammable LCD panels. Masks are well known in lithography, andinclude mask types such as binary, alternating phase-shift, andattenuated phase-shift, as well as various hybrid mask types. An exampleof a programmable mirror array employs a matrix arrangement of smallmirrors, each of which can be individually tilted so as to reflect anincoming radiation beam in different directions. The tilted mirrorsimpart a pattern in a radiation beam which is reflected by the mirrormatrix.

The term “projection system” used herein should be broadly interpretedas encompassing any type of projection system, including refractive,reflective, catadioptric, magnetic, electromagnetic and electrostaticoptical systems, or any combination thereof, as appropriate for theexposure radiation being used, or for other factors such as the use ofan immersion liquid or the use of a vacuum. Any use of the term“projection lens” herein may be considered as synonymous with the moregeneral term “projection system”.

As here depicted, the apparatus is of a transmissive type (e.g.employing a transmissive mask). Alternatively, the apparatus may be of areflective type (e.g. employing a programmable mirror array of a type asreferred to above, or employing a reflective mask).

The lithographic apparatus may be of a type having two (dual stage) ormore substrate tables (and/or two or more patterning device tables). Insuch “multiple stage” machines the additional tables may be used inparallel, or preparatory steps may be carried out on one or more tableswhile one or more other tables are being used for exposure.

Referring to FIG. 1, the illuminator IL receives a radiation beam from aradiation source SO. The source and the lithographic apparatus may beseparate entities, for example when the source is an excimer laser. Insuch cases, the source is not considered to form part of thelithographic apparatus and the radiation beam is passed from the sourceSO to the illuminator IL with the aid of a beam delivery system BDcomprising, for example, suitable directing mirrors and/or a beamexpander. In other cases the source may be an integral part of thelithographic apparatus, for example when the source is a mercury lamp.The source SO and the illuminator IL, together with the beam deliverysystem BD if required, may be referred to as a radiation system.

The illuminator IL may comprise an adjuster AD for adjusting the angularintensity distribution of the radiation beam. Generally, at least theouter and/or inner radial extent (commonly referred to as σ-outer andσ-inner, respectively) of the intensity distribution in a pupil plane ofthe illuminator can be adjusted. In addition, the illuminator IL maycomprise various other components, such as an integrator IN and acondenser CO. The illuminator may be used to condition the radiationbeam, to have a desired uniformity and intensity distribution in itscross-section.

The radiation beam B is incident on the patterning device (e.g., mask)MA, which is held on the support structure (e.g., mask table) MT, and ispatterned by the patterning device. Having traversed the patterningdevice MA, the radiation beam B passes through the projection system PS,which focuses the beam onto a target portion C of the substrate W. Withthe aid of the second positioner PW and position sensor IF (e.g. aninterferometric device, linear encoder or capacitive sensor), thesubstrate table WT can be moved accurately, e.g. so as to positiondifferent target portions C in the path of the radiation beam B.Similarly, the first positioner PM and another position sensor (which isnot explicitly depicted in FIG. 1) can be used to accurately positionthe patterning device MA with respect to the path of the radiation beamB, e.g. after mechanical retrieval from a mask library, or during ascan. In general, movement of the support structure MT may be realizedwith the aid of a long-stroke module (coarse positioning) and ashort-stroke module (fine positioning), which form part of the firstpositioner PM. Similarly, movement of the substrate table WT may berealized using a long-stroke module and a short-stroke module, whichform part of the second positioner PW. In the case of a stepper (asopposed to a scanner) the support structure MT may be connected to ashort-stroke actuator only, or may be fixed. Patterning device MA andsubstrate W may be aligned using patterning device alignment marks M1,M2 and substrate alignment marks P1, P2. Although the substratealignment marks as illustrated occupy dedicated target portions, theymay be located in spaces between target portions (these are known asscribe-lane alignment marks). Similarly, in situations in which morethan one die is provided on the patterning device MA, the patterningdevice alignment marks may be located between the dies.

The depicted apparatus could be used in at least one of the followingmodes:

1. In step mode, the support structure MT and the substrate table WT arekept essentially stationary, while an entire pattern imparted to theradiation beam is projected onto a target portion C at one time (i.e. asingle static exposure). The substrate table WT is then shifted in the Xand/or Y direction so that a different target portion C can be exposed.In step mode, the maximum size of the exposure field limits the size ofthe target portion C imaged in a single static exposure.2. In scan mode, the support structure MT and the substrate table WT arescanned synchronously while a pattern imparted to the radiation beam isprojected onto a target portion C (i.e. a single dynamic exposure). Thevelocity and direction of the substrate table WT relative to the supportstructure MT may be determined by the (de-)magnification and imagereversal characteristics of the projection system PS. In scan mode, themaximum size of the exposure field limits the width (in the non-scanningdirection) of the target portion in a single dynamic exposure, whereasthe length of the scanning motion determines the height (in the scanningdirection) of the target portion.3. In another mode, the support structure MT is kept essentiallystationary holding a programmable patterning device, and the substratetable WT is moved or scanned while a pattern imparted to the radiationbeam is projected onto a target portion C. In this mode, generally apulsed radiation source is employed and the programmable patterningdevice is updated as required after each movement of the substrate tableWT or in between successive radiation pulses during a scan. This mode ofoperation can be readily applied to maskless lithography that utilizesprogrammable patterning device, such as a programmable mirror array of atype as referred to above.

Combinations and/or variations on the above described modes of use orentirely different modes of use may also be employed.

Arrangements for providing liquid between a final element of theprojection system PS and the substrate can be classed into three generalcategories. These are the bath type arrangement, the so-called localizedimmersion system and the all-wet immersion system. In the bath typearrangement substantially the whole of the substrate W and optionallypart of the substrate table WT is submersed in a bath of liquid.

The localized immersion system uses a liquid supply system in whichliquid is only provided to a localized area of the substrate. The spacefilled by liquid is smaller in plan than the top surface of thesubstrate and the area filled with liquid remains stationary relative tothe projection system PS whilst the substrate W moves underneath thatarea. FIGS. 2-5 show different supply devices which can be used in sucha system. Sealing features are present to seal liquid to the localizedarea. One way which has been proposed to arrange for this is disclosedin PCT patent application publication no. WO 99/49504.

In the all wet arrangement the liquid is unconfined. The whole topsurface of the substrate and all or part of the substrate table iscovered in immersion liquid. The depth of the liquid covering at leastthe substrate is small. The liquid may be a film, such as a thin film,of liquid on the substrate. Immersion liquid may be supplied to or inthe region of a projection system and a facing surface facing theprojection system (such a facing surface may be the surface of asubstrate and/or a substrate table). Any of the liquid supply devices ofFIGS. 2-5 may be used in such a system. However, sealing features arenot present, are not activated, are not as efficient as normal or areotherwise ineffective to seal liquid to only the localized area.

As illustrated in FIGS. 2 and 3, liquid is supplied by at least oneinlet onto the substrate, preferably along the direction of movement ofthe substrate relative to the final element. Liquid is removed by atleast one outlet after having passed under the projection system PS.That is, as the substrate is scanned beneath the element in a −Xdirection, liquid is supplied at the +X side of the element and taken upat the −X side. FIG. 2 shows the arrangement schematically in whichliquid is supplied via inlet and is taken up on the other side of theelement by outlet which is connected to a low pressure source. In theillustration of FIG. 2 the liquid is supplied along the direction ofmovement of the substrate W relative to the final element, though thisdoes not need to be the case. Various orientations and numbers of in-and out-lets positioned around the final element are possible; oneexample is illustrated in FIG. 3 in which four sets of an inlet with anoutlet on either side are provided in a regular pattern around the finalelement. Note that the direction of flow of the liquid is shown byarrows in FIGS. 2 and 3.

A further immersion lithography solution with a localized liquid supplysystem is shown in FIG. 4. Liquid is supplied by two groove inlets oneither side of the projection system PS and is removed by a plurality ofdiscrete outlets arranged radially outwardly of the inlets. The inletscan be arranged in a plate with a hole in its centre and through whichthe projection beam is projected. Liquid is supplied by one groove inleton one side of the projection system PS and removed by a plurality ofdiscrete outlets on the other side of the projection system PS, causinga flow of a thin film of liquid between the projection system PS and thesubstrate W. The choice of which combination of inlet and outlets to usecan depend on the direction of movement of the substrate W (the othercombination of inlet and outlets being inactive). Note that thedirection of flow of fluid and of the substrate W is shown by arrows inFIG. 4.

Another arrangement which has been proposed is to provide the liquidsupply system with liquid confinement structure which extends along atleast a part of a boundary of the space between the final element of theprojection system and the substrate table. Such an arrangement isillustrated in FIG. 5.

FIG. 5 schematically depicts a localized liquid supply system or fluidhandling structure with a liquid confinement structure 12, which extendsalong at least a part of a boundary of the space 11 between the finalelement of the projection system PS and a facing surface (e.g. thesubstrate table WT or substrate W). (Please note that reference in thefollowing text to surface of the substrate W also refers in addition orin the alternative to a surface of the substrate table WT, unlessexpressly stated otherwise.) The liquid confinement structure 12 issubstantially stationary relative to the projection system PS in the XYplane though there may be some relative movement in the Z direction (inthe direction of the optical axis). In an embodiment, a seal is formedbetween the liquid confinement structure 12 and the surface of thesubstrate W and may be a contactless seal such as a gas seal (such asystem with a gas seal is disclosed in United States patent applicationpublication no. US 2004-0207824) or fluid seal.

The liquid confinement structure 12 at least partly contains liquid inthe space 11 between a final element of the projection system PS and thesubstrate W. A contactless seal, such as a gas seal 16, to the substrateW may be formed around the image field of the projection system PS sothat liquid is confined within the space 11 between the substrate Wsurface and the final element of the projection system PS. The space 11is at least partly formed by the liquid confinement structure 12positioned below and surrounding the final element of the projectionsystem PS. Liquid is brought into the space 11 below the projectionsystem PS and within the liquid confinement structure 12 by liquid inlet13. The liquid may be removed by liquid outlet 13. The liquidconfinement structure 12 may extend a little above the final element ofthe projection system PS. The liquid level rises above the final elementso that a buffer of liquid is provided. In an embodiment, the liquidconfinement structure 12 has an inner periphery that at the upper endclosely conforms to the shape of the projection system PS or the finalelement thereof and may, e.g., be round. At the bottom, the innerperiphery closely conforms to the shape of the image field, e.g.,rectangular, though this need not be the case.

The liquid may contained in the space 11 by the gas seal 16 which,during use, is formed between the bottom of the liquid confinementstructure 12 and the surface of the substrate W. The gas seal 16 isformed by gas, e.g. air or synthetic air but, in an embodiment, N₂ oranother inert gas. The gas in the gas seal 16 is provided under pressurevia inlet 15 to the gap between liquid confinement structure 12 andsubstrate W. The gas is extracted via outlet 14. The overpressure on thegas inlet 15, vacuum level on the outlet 14 and geometry of the gap arearranged so that there is a high-velocity gas flow inwardly thatconfines the liquid. The force of the gas on the liquid between theliquid confinement structure 12 and the substrate W contains the liquidin a space 11. The inlets/outlets may be annular grooves which surroundthe space 11. The annular grooves may be continuous or discontinuous.The flow of gas is effective to contain the liquid in the space 11. Sucha system is disclosed in United States patent application publicationno. US 2004-0207824, which is hereby incorporated by reference in itsentirety. In another embodiment, the liquid confinement structure 12does not have a gas seal.

FIG. 6 illustrates a liquid confinement structure 12 which is part of aliquid supply system. The liquid confinement structure 12 extends aroundthe periphery (e.g., circumference) of the final element of theprojection system PS.

A plurality of openings 20 in the surface which defines the space 11provide the liquid to the space 11. The liquid passes through openings29, 20 in side walls 28, 21 respectively prior to entering the space 11.

A seal is provided between the bottom of the liquid confinementstructure 12 and the substrate W. In FIG. 6 a seal device is configuredto provide a contactless seal and is made up of several components.Radially outwardly from the optical axis of the projection system PS,there is provided a (optional) flow control plate 50 which extends intothe space 11. Radially outwardly of the flow control plate 50 on thebottom surface of the liquid confinement structure 12 facing thesubstrate W or substrate table WT may be an opening 180. The opening 180can provide liquid in a direction towards the substrate W. Duringimaging this may be useful in preventing bubble formation in theimmersion liquid by filling a gap between the substrate W and substratetable WT with liquid.

Radially outwardly of the opening 180 may be an extractor assembly 70 toextract liquid from between the liquid confinement structure 12 and thesubstrate W and/or the substrate table WT. The extractor assembly 70 mayoperate as a single phase or as a dual phase extractor.

Radially outwardly of the extractor assembly 70 may be a recess 80. Therecess 80 is connected through an inlet 82 to the atmosphere. The recess80 may be connected via an outlet 84 to a low pressure source. Radiallyoutwardly of the recess 80 may be a gas knife 90. An arrangement of theextractor assembly, recess and gas knife is disclosed in detail inUnited States patent application publication no. US 2006/0158627incorporated herein in its entirety by reference.

The extractor assembly 70 comprises a liquid removal device or extractoror inlet such as the one disclosed in United States patent applicationpublication no. US 2006-0038968, incorporated herein in its entirety byreference. In an embodiment, the liquid removal device 70 comprises aninlet which is covered in a porous material 110 which is used toseparate liquid from gas to enable single-liquid phase liquidextraction. An under pressure in chamber 120 is chosen is such that themeniscuses formed in the holes of the porous material 110 preventambient gas from being drawn into the chamber 120 of the liquid removaldevice 70. However, when the surface of the porous material 110 comesinto contact with liquid there is no meniscus to restrict flow and theliquid can flow freely into the chamber 120 of the liquid removal device70.

The porous material 110 has a large number of small holes each with adimension, e.g. a width, such as a diameter, in the range of 5 to 50 μm.The porous material 110 may be maintained at a height in the range of 50to 300 μm above a surface from which liquid is to be removed, e.g. thesurface of a substrate W. In an embodiment, porous material 110 is atleast slightly liquidphilic, i.e. having a dynamic contact angle of lessthan 90°, desirably less than 85° or desirably less than 80°, to theimmersion liquid, e.g. water.

Although not specifically illustrated in FIG. 6, the liquid supplysystem has an arrangement to deal with variations in the level of theliquid. This is so that liquid which builds up between the projectionsystem PS and the liquid confinement structure 12 can be dealt with anddoes not spill. One way of dealing with this liquid is to provide aliquidphobic (e.g., hydrophobic) coating. The coating may form a bandaround the top of the liquid confinement structure 12 surrounding theopening and/or around the last optical element of the projection systemPS. The coating may be radially outward of the optical axis of theprojection system PS. The liquidphobic (e.g., hydrophobic) coating helpskeep the immersion liquid in the space 11.

The examples of FIGS. 5 and 6 are a so called localized area arrangementin which liquid is only provided to a localized area of the top surfaceof the substrate W at any one time. Other arrangements are possible,including fluid handling systems which make use of a gas drag principle.The so-called gas drag principle has been described, for example, inUnited States patent application publication nos. US 2008-0212046, US2009-0279060 and US 2009-0279062. In that system the extraction holesare arranged in a shape which desirably has a corner. The corner may bealigned with the stepping and scanning directions. This reduces theforce on the meniscus between two openings in the surface of the fluidhanding structure for a given speed in the step or scan directioncompared to if the two outlets were aligned perpendicular to thedirection of scan. An embodiment of the invention may be applied to afluid handling structure used in all wet immersion apparatus. In the allwet embodiment, fluid is allowed to cover the whole of the top surfaceof the substrate table, for example, by allowing liquid to leak out of aconfinement structure which confines liquid to between the final elementof projection system and the substrate. An example of a fluid handlingstructure for an all wet embodiment can be found in United States patentapplication publication no. US 2010-0060868.

As will be appreciated, any of the above described features can be usedwith any other feature and it is not only those combinations explicitlydescribed which are covered in this application.

There is a risk that the meniscus between the fluid handling structureand the facing surface of the substrate may be unstable. Immersionliquid, for example in a localized immersion system, may escape from theimmersion space 11. The escaped liquid may take the form of a droplet ora film of liquid. Reference herein to droplet includes reference to filmunless indicated to the contrary. Note that in many situations a filmwould break into one or more droplets as the droplet evaporates, ormoves.

A liquid droplet outside the immersion space may pose a risk tooperation of an immersion system. A droplet may increase defectivity ofan immersion system. Liquid may evaporate from the droplet applying aheat load to the surface on which the droplet is situated. Such asurface could include a sensor where the heat load may distort acomponent of the sensor, deleteriously affecting accurate measurements.Such a sensor may be part of a positioning system, so distortion of thesensor could affect system positioning and overlay. Where the surface isa surface of a substrate, the heat load may cause the substrate todeform, for example contract the surface, affecting the accurateexposure and hence overlay. The droplet may transport a contaminant,such as a contaminant from a substrate coating, around the immersionsystem. On evaporating, the droplet may leave a contaminant on a surfaceof a substrate causing an imaging defect, or a drying stain. The dropletmay be situated on a location which later passes under the fluidhandling structure. On contact with the meniscus, for example as acollision, the droplet may cause the formation of a bubble within theimmersion space. Such a bubble may interfere with exposure affecting thesuccessful imaging of a pattern on a substrate during exposure.

A droplet may pose a particular risk to a multi-stage (or multi-table)immersion lithographic tool. For example, the droplet may be lost fromthe immersion space 11 during substrate swap (i.e., the process by whicha substrate is replaced after exposure) when an immersion liquid is keptin contact with the projection system PS. For example, at the beginningof substrate swap, the substrate table WT supporting the substrate W isunder the fluid handling structure 12. A surface of the substrate tablehelps serve to form the space 11. The substrate table WT is moved to aposition at which the substrate W can be removed and a new substrateplaced on the substrate table for exposure. As the substrate table ismoved, it moves away from the projection system PS, from under the fluidhandling structure 12. To keep immersion liquid in the space 11, thesurface of the substrate table is replaced by a shutter surface of ashutter member. The shutter surface and the substrate table may be movedin together in one motion. From the perspective of the immersion space11, the shutter surface and the surface of the substrate table serve toprovide a substantially continuous surface. The shutter surface helpsserve to form the space 11.

The shutter surface may take the form of a surface of a second table,such as a swap table. The second table may be a further substrate tableWT2 as shown in FIGS. 7, 8, 10 and 11, or a measurement table MT asshown in FIGS. 9 and 12. The measurement table MT is designed not tosupport a substrate W; so, the measurement table may be considered to beunable to support a substrate W. The measurement table may have one moreoptical sensors 21 to detect a property of the projection system. It mayhave a cleaning station 22 to clean the surface of the projection systemin contact with immersion liquid, or a feature of the fluid handlingstructure 12, or both.

In an embodiment, the tables WT, WT2, MT may not meet, as shown in FIGS.7, 8 and 12. When the tables are positioned to be as close as possible,there may be a gap between them. This may be desirable to preventcollision between the tables. It is more likely that the tables do notmeet if both are substrate tables as shown in FIGS. 7 and 8 becausesubstrate tables may be required to be positioned more accurately than ameasurement table to achieve accurate positioning of the substrate.Accurate positioning of a table may require a large positioning systemto be associated with the table, making the table difficult to positionclosely next to another substrate table. The accurate positioningequipment may be more sensitive and thus more at risk of damage oncollision.

In an embodiment, the shutter surface may take the form of a fixedextension or moveable extension (e.g., a telescoping arm) of thesubstrate table WT. In an embodiment, the shutter surface may take theform a closing plate or disk that is separable from the tables WT, WT2,MT and that may be connected to the fluid handling structure while thetables WT, WT2, MT move with respect thereto.

The shutter surface may include a removable bridge 24 to bridge the gapbetween the surfaces of the tables (as described in U.S. patentapplication publication no. US 2009/0296065, which is herebyincorporated by reference in its entirety). The removable bridge 24 maybe positionable between the tables WT, WT2, MT during, for example,substrate swap. The surface of the bridge 24 is moved under the fluidextraction surface, as represented by a liquid footprint 26 as shown inFIGS. 7 and 8.

The liquid footprint 26 may represent an area of the substrate,substrate table WT or shutter member which is in contact with theimmersion liquid of the space 11 at a moment in time. With respect tothe surfaces of the tables WT, WT2, MT and the removable bridge 24, theliquid footprint moves from one table to the other over the removablebridge 24, as shown by arrow 27. (In the frame of reference of theprojection system PS and the fluid handling structure it is the tablesWT, WT2, MT and the removable bridge which are moving.) The liquidfootprint has a dimension, i.e. width 30, which is substantiallyperpendicular to the direction of relative motion 27.

In an embodiment, an edge of the substrate table WT, for example theentire periphery of the substrate table WT, may be part of a positioningsystem configured to position the substrate table WT, and thus substrateW, relative to the projection system PS. The part of the positioningsystem may be a positioning plate with one or more positioning markers,such as an encoder grid 32, along the edge of the substrate table WT.

FIGS. 8, 9, 11 and 12 all show different arrangements in which thesubstrate table has an encoder grid 32 along all or part of its edge.FIG. 8 shows a dual substrate table arrangement with a removable bridge24 in which both substrate tables have an encoder grid along theiredges. In FIG. 12 there is a substrate table with an encoder grid and ameasurement table MT with a removable bridge therebetween. Themeasurement table MT may have an encoder grid. Note that where accuratepositioning of the measurement table is not required it may not bedesirable to have a measurement table with an encoder grid. Accuratepositioning is desirable for the substrate table WT, WT2 as accuratepositioning is required for exposure of an image onto a substrate. FIGS.9 and 11 are the same as FIGS. 8 and 12, respectively, except withoutthe removable bridge.

In exchanging tables beneath the fluid handling structure 12, as shownin FIG. 8, the liquid footprint 26 crosses the encoder grid 32. Anencoder grid 32 operates with an encoder sensor positioned in adifferent frame of reference such as the same frame of reference as theprojection system. As the substrate table moves, the encoder sensor maysense the relative movement of the substrate table. The sensor maydirect a radiation beam at the encoder grid and detect the radiationredirected (e.g., reflected) back by the encoder grid 32.

To work effectively it is desirable that the surface of the encoder grid32 is clean. So it is undesirable that a droplet escapes from theimmersion space 11 onto the grid. The droplet may be source ofdefectivity, for example in distorting a dimension of the grid and/orobstructing the radiation beam of the encoder sensor either as a dropletor in the form of a contamination particle the droplet may have leftbehind. Liquid cannot be prevented from contacting the grid during, forexample, substrate swap as the liquid footprint 26 passes over thesurface of the grid 32. A droplet may escape from the immersion space 11in any direction of the surface surrounding the liquid footprint 26.

It would be desirable to help prevent a droplet from escaping onto thesurface of the grid, especially in a direction 34. Direction 34 has acomponent perpendicular to the direction of relative motion 27. Where aremovable bridge 24 is used to bridge a gap between two tables, there isa risk that a droplet escaping in direction 34 may cross an edge 36 ofthe removable bridge 24. A droplet crossing the edge 36 escapes theimmersion system and may land on a component which is unsuited tocontacting immersion liquid. The liquid may damage the component. It istherefore desirable to provide a transfer lane 38 which restricts themotion of a droplet escaping from the immersion space to move indirection 34.

FIGS. 13, 14 and 15 show three different embodiments of transfer lane 38which may be present in the embodiments shown in FIGS. 7 to 12. In FIG.13, a removable bridge 24 is located between two tables WT, MT, WT2.Neither of the tables WT, MT, WT2 has a grid 32 along its edges. Thisembodiment may be present in FIG. 7. The embodiment of FIG. 10 is thesame as described here, except without the removable bridge 24. Thesurface of the removable bridge 24 provides at least a part of thesurface of the transfer lane 38 (or transfer surface). A portion 44, 46of each table WT, MT, WT2 aligned with the surface of the removablebridge 24 may each provide a part of the surface of the transfer lane38. The portions 44, 46 may have the same surface features of the restof the transfer lane 38, i.e., the surface of the removable bridge.Between one or both tables WT, MT, WT2 and the removable bridge 24 maybe a gap 40 which is either sealed during relative motion 27 to preventliquid passing into the gap or has a fluid extraction device to removeany liquid which flows into the gap.

FIG. 14 shows the transfer lane 38 of the embodiment shown in FIG. 8. Ithas the same features as FIG. 13 except as described otherwise. In thisembodiment an encoder grid 32 is present along the edge of the substratetable WT and is optionally present on the edge of the other table WT2,MT. It corresponds to the embodiments shown in FIGS. 9 and 11. Aremovable bridge 24 is not present so the surface of the transfer lane38 is provided by edge portions 44, 46 of the two tables WT, WT2, MT.Between the tables WT, MT, WT2 may be a gap 40 which is either sealedduring relative motion 27 to prevent liquid passing into the gap or hasa fluid extraction device to remove any liquid which flows into the gap.

FIG. 15 shows a combination of the embodiments shown in FIGS. 13 and 14.It may correspond to a part of the embodiments shown in FIGS. 8 and 12which have a removable bridge 24 and at least one of the tables MT, WT,WT2 has an encoder grid 32 along an edge which in use moves under thefluid handling structure 12. The transfer lane 38 has at least threeelements: the surface of the removable bridge 24 and the surface of theportions 44, 46 of each table WT, WT2, MT aligned with the removablebridge 24.

In each embodiment, each part of the transfer lane 38 (which may includeat least one surface selected from: the surface of the removable bridge24, the portion 44 and/or the portion 46) may be located under the pathof a liquid footprint 26 during substrate swap. The transfer lane 38 hasa width 48 which is at least as wide as the liquid footprint 26. Asshown the transfer lane 38 may be as wide as the removable bridge, butto prevent a droplet from moving beyond an edge of the removable bridgethe width of the removable bridge may be larger than the width 48 of thetransfer lane 38.

The transfer lane 38 may have a lyophobic surface with respect to theimmersion liquid, for example it may be hydrophobic when the immersionliquid is water. The surface of the transfer lane 38 may have arelatively high contact angle, for example more than 90 degrees as astatic contact angle, or more than 75 degrees as a receding contactangle, which helps to prevent a droplet from remaining on the surface ofthe transfer lane 38. Such a surface may improve the ease of control ofthe meniscus between the fluid handling structure and the surface of thetransfer lane 38. The surface may be resistant to the exposureradiation, or corrosion by the immersion liquid, or both. The surfacecontact angle may therefore retain its contact angle under the influenceof exposure radiation and immersion liquid corrosion, separately or incombination. The surface may be a coating as described in U.S. patentapplication publication no. US 2009/0206304, which is herebyincorporated by reference in its entirety.

To prevent a droplet from moving in direction 34, the transfer lane 38may have a barrier. The barrier may prevent motion in the direction 34.As described herein the barrier may include the feature of a surfacecoating, or a topographical feature, or a fluid extraction device, orany combination of the foregoing. The transfer lane 38 may have twobarriers. Each barrier may be substantially parallel to the transferlane, may be substantially parallel to the direction of relative motion27, or both. In an embodiment each barrier is associated, e.g.substantially aligned, with an edge of the transfer lane 38. Thebarriers may define the width 48 of the transfer lane.

FIGS. 16 to 19 show different embodiments of transfer lanes with abarrier. The Figures are intended to indicate possible embodiments oftransfer lane 38 with the barrier. It is not intended that all possibleembodiments are limited to those represented in these Figures. In FIGS.16 to 19, ‘A’ denotes the position of the gap 40 between the twoportions 44 and 46 of the embodiment shown in FIG. 14. ‘B’ denotes thepositions of the gaps 40 between the removable bridge 24 and each of theportions 44 and 46.

FIG. 16 depicts in plan a transfer lane 38 with a barrier 50. There is abarrier associated with each edge 52 of the transfer lane 38. In anembodiment, each barrier 50 is a ridge, or protrusion. In an embodiment,the barrier 50 may be located at an edge 52. In an embodiment, a barrier50 is located inwardly from an edge 52; the distance between the twobarriers 50 on opposite sides of the transfer lane 38 is at least as thewidth of the liquid footprint 26. This is desirable because contact of abarrier 50 with the liquid meniscus of the footprint 26 may pin themeniscus and increase the risk of droplet loss. The surface of thebarrier 50 may protrude above the surface of the transfer lane 38 so asto help to block the flow of immersion liquid towards or past the edge52. A raised barrier 50 may have a sharp corner in profile in adirection perpendicular to the direction of relative motion 27. Thecorner may help serve to pin the meniscus of a droplet of immersionliquid, helping to prevent it from flowing towards or past an edge 52.An edge 52 may correspond in part to the edge 36 of the removable bridge24. In an embodiment, the barrier 50 may be an edge 52 with a sharpcorner preventing liquid from flowing over the edge 52.

In an embodiment, the barrier member 50 may have a recess 56 (or groove)recessed relative to the surface of the transfer lane 38. The recess mayhave a sharp corner, in profile, to pin an immersion liquid meniscus,for example, of a droplet. The corner of the recess may function in thesame manner as a ridge in helping to prevent the flow of the immersionliquid away from footprint 27 towards or past an edge 52.

In an embodiment, as shown in FIG. 17, the barrier 50 may have aplurality of ridges 54 each of which may have the features as describedwith respect to the embodiment of FIG. 16. Between adjacent ridges theremay be at least a recess 56. In an embodiment the barrier 50 may have aplurality of recesses 56 and at least a ridge 54. A plurality ofparallel features (e.g., recess 56 and/or ridge 54) may help prevent adroplet from reaching the edge 52 of the transfer lane 38. If thedroplet passes beyond a first feature in the barrier 50 in direction 34,a feature closer to the edge 52 may prevent the droplet moving closer tothe edge 52. As liquid meniscus is pinned by a corner of a recess orridge, it may be desirable to have more than one recess or ridge. Therecess and ridge corners further towards the edge 52 of the transferlane 38 may serve to help prevent liquid, which passes a recess or ridgecorner further from the edge 52, from reaching the edge 52.

In an embodiment, the surface of a recess or ridge protrudes not morethan 2 mm above the surface of the transfer lane 38. So that the pinningof the edges of the recess and/or ridge is achieved, the surface of arecess or ridge protrudes at least 10 μm above the surface of thetransfer lane 38. In an embodiment, such as for a localized immersionsystem, the surface of the barrier is in the range of 10 μm to 150 μm,desirably in the range of 20 μm to 100 μm. The reason for the lowmaximum in this embodiment is to help avoid machine damage caused by acollision between the confinement structure 12 and the surface of thetransfer lane 38. In an embodiment, a machine damage control system ispresent which may operate to help ensure the confinement structure 12avoids, and so does not collide with, the surface of the transfer lane38.

Although this part of the description refers to topographical features,the barrier 50 may additionally or alternatively have a feature which isformed by a variation in surface contact angle. For example, there maybe region of increased lyophobicity (e.g., hydrophobicity) 50′ to pinimmersion liquid, helping to prevent the liquid from reaching or movingpast the edge 52. There may be an area of reduced lyophobicity (e.g.,hydrophobicity) 50′ (i.e., increased lyophilicity (e.g.,hydrophilicity)) to retain immersion liquid. The region of increasedlyophilicity may be provided by a photo-catalytic material such astitanium oxide, as described in U.S. Pat. No. 7,450,217 and U.S. patentapplication publication no. US 2010-0060870, both of which are herebyincorporated in their entirety by reference. One or more regions ofdiffering lyophobicity may be arranged in parallel elongate regions asshown in and described with reference to FIG. 17 for topographicalfeatures.

In an embodiment, the use of a barrier 50 is suitable for use in anall-wet immersion system. In an all wet system the liquid confinementstructure 12 allows liquid to escape from the space between under theundersurface of the liquid confinement structure 12. The barrier 50helps prevent immersion liquid from escaping past the edge of thetransfer lane 38 as the transfer lane moves under the liquid confinementstructure 12. In operation of such an arrangement the liquid supply maybe reduced or even stopped as the transfer lane passes under the liquidconfinement structure 12. Once the transfer lane has passed under theconfinement structure 12 it is replaced by the surface of a table WT2,MT where the supply of immersion liquid is increased, for examplereturned to its previous rate of supply. As more liquid may flow out ofthe liquid confinement structure 12 of an all-wet immersion system thanof a localized immersion system, the dimensions of the barrier 50 may belarger than in a localized immersion system. For example the distancebetween ridges or recesses may be between 0.01 and 1 mm, and theirheight may be in the range of 10 μm to 1 mm, for example 0.5 mm.

FIGS. 18 and 19 show embodiments having fluid extraction features. FIG.18 shows two tables without a removable bridge 24. The transfer lane 38is defined by two portions 44, 46, one of each table WT, MT, WT2. At theedge of the transfer lane is a fluid extraction opening 56 for theextraction of a fluid including immersion liquid. Each fluid extractionopening 56 is arranged to extract liquid which may move from thetransfer lane 38 with in direction 34. Thus liquid moving in direction34 is removed before it moves off the transfer lane onto, for example,the surface of a grid 32. In an embodiment, the fluid extraction opening56 may be formed in or on the top of a ridge 54.

Each extraction opening 56 is formed in the surface of the respectivetable WT, WT2, MT and may be connected to an underpressure source (notshown). The underpressure source may operable as the portion 44, 46adjacent the fluid extraction opening 56 passes under the fluid handlingstructure 12. Limiting the operation of the fluid extraction opening 56in this way means that extraction flow only occurs when it is required.This may be desirable because the extraction flow may apply a heat loadto the opening and the surrounding part of the table WT, WT2, MT,especially when the fluid flow comprises liquid and gas in a two phaseflow. The liquid may evaporate into the gas in the two phase fluid,applying a heat load, for example, by absorbing heat from itssurroundings. By supplying heat, the surroundings which form part of thelithographic apparatus may distort. To counteract the heat load, aconduit connecting the fluid extraction opening 56 to the underpressuresource may be insulated from the surroundings. To achieve this theadjacent portion 44, 46 may be insulated.

Additionally or alternatively a heat source such as a heat pipe orheating element may be present in the table around the fluid extractionopening 56 to counteract the heat load. A controller with a temperaturesensor may be present with heat source to ensure that the heat appliedis regulated, a stable temperature is achieved or both. The heat sourcemay be located at least under the portions 44, 46. It may be desirablefor the portions 44, 46 to have a controlled heat source and or beinsulated as such features can be used to counteract a heat load appliedby a droplet remaining on the transfer lane 38 after passing under theliquid footprint.

FIG. 19 shows the same features as FIG. 7, except with a removablebridge 24. In an embodiment, the surface of the removable bridge is notinsulated from the rest of the bridge and does not have a controlledheat source. In another embodiment the surface is insulated from therest of the bridge 24, the bridge has a controlled heat source, or both.

In each of the embodiments shown in FIGS. 13 to 19, the surface of thetransfer lane 38 or at least a portion of the transfer lane 26, 44, 46may have a one dimensional lyophobic surface, such as a one dimensionalsuperhydrophobic surface. Such a surface may have a ridged structurewith the ridge pitch of between 100 and 1000 nm. A roughness factor (Rf)may be defined as the ratio between the area of a surface which contactsa liquid droplet resting on the surface and the area of the surfacewhich the droplet covers. For an embodiment of the surface, theroughness factor may be greater or equal to one, desirably less than 1.5and close to one. The width of a ridge may be approximately, if notsubstantially, the same as the width of a recess or groove between twoadjacent ridges. In an embodiment, the width of the ridge is exceeded bythe width of the recess or groove between two adjacent ridges. The widthof a ridge may be less than the height or depth of the ridge. In anembodiment the width of a ridge is in the range of 0.4 to 0.6 of theheight or depth of a ridge. In an embodiment the height of a ridge maybe twice as large as the width of a ridge. The width of the ridges, ator near the top of the ridges (which would contact the liquid of adroplet resting on the surface), is in the range of 50 nm to 50 μm,desirably less than 20 μm, less than 10 μm, less than 5 μm, or less than1000 nm (i.e. submicron). Such a ridged or grooved surface may exhibit agreater lyophobic property along one direction in the plane of thesurface than in a perpendicular direction in the plane.

Desirably, the orientation of maximum lyophobicity corresponds to thedirection perpendicular to the relative movement between the liquidconfinement structure 12 and the respective table MT, WT, WT2, as shownby arrow 27. The direction of arrow 27 may correspond to the directionof the ridged structure of the surface. In the reference frame of motionof the transfer lane 38, as the footprint 26 travels over the transferlane 38, the meniscus of the footprint travels along the ridges andgrooves of the textured structure on the transfer lane surface. Sincethe movement of the transfer lane 38 under the space 11 is in thedirection of arrow 27, the maximum lyophobic property that the surfacemay exhibit relative to the liquid in the space 11 may occur during suchrelative motion. By having such a one dimensional surface, the desiredlyophobic property of a surface may be exhibited in a direction whereits use is most desirable. Desirably, a higher relative motion betweenthe projection system and the facing surface may be achieved with acertain liquid loss. At a certain velocity of relative motion themeniscus stability is improved and the risk of bubble inclusion into theliquid of the immersion space 11 may be reduced.

In an embodiment, the surface of a one dimensional lyophobic surface isridged. The grid 32 also has a ridge like surface where the ridges areperiodic, desirably with a determined, regular spacing. Therefore theintrinsic surface geometry of the grid 32 may provide the surface with alyophobic property as well as the measurable geometry. Since a ridgeshould be desirably twice as deep as wide to achieve the desired effectwith an immersion liquid of water, a ridge width of 10 μm may have adepth of 20 μm. A ridge geometry with shallower depth may provide asurface with less lyophobic surface. Material used to make the grid 32,for example a Zerodur® ceramic, may normally have a lyophilic contactangle. To ensure that the surface of the grid is lyophobic, the grid 32may have a lyophobic coating that is less than 100 nm, desirably lessthan 40 nm, for example in the range of 1 to 20 nm. The coatingthickness is desirably small to reduce the loss in optical transmissionthrough the coating. The coating may be conformal, i.e. conforming tothe topography of the surface onto which it is applied or located.

In an embodiment, the surface which interacts with the immersion liquidis an optically transparent plate which covers the grid 32. The plate isdesirably transparent for the operating wavelength of the encodersensor. A material such as a glass or quartz may be used to make theplate. The surface of the plate may be formed of sub-micron (e.g. withpitch 10 to 100 nm) texture formed from a coating. There may be a riskthat such a structure may interfere with radiation used for encodermeasurement. However, the structure may have features dimensionedrelative to the wavelength of the encoder radiation so that it does notinterfere with the encoder radiation. Care may be taken because astructure with the described pitch range may be at risk of causingcontamination and/or of being contaminated, preventing effectivefunctioning of the encoder measurement. The structure may be of asubmicron scale. A contaminating particle from a substrate coating maytend to be larger, of a micron scale. Therefore a particle larger thanthe width of a submicron structure such as a groove (or other recessedstructure) is less likely to contaminate such a submicron feature than amicron scale feature of the structured surface.

FIG. 20 is a plan view of a substrate table WT, WT2 with a grid 32. Inan embodiment, the grid is present along each edge of the substratetable. The portion 44, 46 of the transfer lane 38 crosses a part of thegrid along an edge of the substrate table. As there is a risk that adroplet, resulting contamination, or both remains on the portion 44, 46after it passes under the fluid handling structure, performance of thepart of the grid 32 corresponding to the portion 44, 46 may bedetrimentally affected. It may prevent accurate positioning to beachieved from measurements to be made from that part of the grid 32.

FIG. 23 shows an arrangement of a substrate table WT, WT2 with a grid 32around its periphery. The substrate table WT, WT2 has four edges 72.Associated with each edge 72 is a portion of the grid 32. Associatedwith each edge 72 is an encoder sensor 74. The encoder sensors 74 eachmay have a plurality of detectors 76 which may be arranged in a column.The column may be located perpendicular to the associated substratetable edge 72. As the substrate table WT, WT2 is moved, different one ormore of the detectors 76 in the encoder sensor 74 may be used to detectthe location of the associated grid 32 and therefore the location of thesubstrate table. By having an encoder sensor 74 associated with oppositeedges 72 of the table (for example, edges X′ and X″ which indicate theportion of the table which can achieve maximum displacement along an Xaxis relative to the projection system), one of the encoder sensors 74associated with one or both edges X′ and X″ will be located over aportion of the grid 32 whatever the position of the substrate table WT,WT2. The same applies to the encoder sensors 74 associated with theedges 72 aligned with the orthogonal axis in the plane of the substratetable WT, WT2, for example edges Y′ and Y″ of the substrate table, whenmoved relative to the projection system. By measurements made with anencoder sensor 74 in the X axis and an encoder sensor 74 in the Y axis,the location of the substrate table WT, WT2 relative to the projectionsystem in the plane of the surface of the substrate table WT, WT2 may bedetermined.

As shown in FIG. 23 a portion of the grid 32 on the X′ edge of thesubstrate table WT, WT2 is not beneath a detector 76 of the associatedencoder sensor 74. Therefore the measurement in the X axis should bemade using the grid on the X″ edge of the substrate table WT, WT2.However, when the portion 44, 46 of the transfer lane 38 crosses thegrid 32, a part of the grid 32 may be covered by a droplet or acontaminating particle may obscure part of the grid 32 so a measurementof the grid 32 cannot or should not be made by the encoder sensor 76 onthe X″ edge.

To help prevent inaccurate positioning, measurements may be taken fromlocations of the grid 32 away from the transfer lane 38. To ensureaccurate positioning is still achieved, an extra encoder sensor 75, or areserve sensor, may be used. The reserve sensor 75 may have the samefeatures as the encoder sensor 74 of the X″ edge, except that it isdisplaced from the X″ encoder sensor 74 by a distance which at leastexceeds the width of the transfer lane 38 along the X″ edge. The reservesensor 75 may operate when the X″ encoder sensor 74 is located above theportion 44, 46 (and vice versa the X″ encoder sensor 74 may operate whenthe reserve sensor 75 is located above the portion 44, 46). Such anarrangement is shown, for example, in FIG. 24 in which the X″ encodersensor 74 and the reserve sensor 75 are spaced away from the projectionsystem in the Y axis, along the X″ edge 72 by a similar distance. Theuse of the reserve sensor 75 obviates the need to take measurements froma part of the grid 32 located in the transfer lane 38 and/or by anencoder sensor 74 located on the X′ edge.

In an embodiment, the portion 44, 46 may be opaque to the radiation usedby the positioning system for the detectors to detect the grid 32. In anembodiment, the grid 32 is absent from the transfer lane 38. As the useof the reserve sensor 75 and/or the encoder sensor 74 located on the X′edge obviates the need to take measurements from the portion of the gridplate 32 in the transfer lane 38, there can be a gap 43 in the grid 32corresponding to the transfer lane 38. Such an embodiment is shown inFIG. 21 which corresponds to a cross-section of the substrate table WT,WT2 along the line X-X. The surface 60 of the substrate table WT, WT2(hereinafter referred to as the surrounding surface 60) is substantiallythe same height as the transfer lane 38. FIG. 22 shows a cross-sectionof the substrate table WT, WT2 along the line Y-Y. The surface 60 of thesubstrate table WT, WT2 is substantially co-planar with the surface ofthe grid plate 32, as shown in FIG. 22. In this arrangement a dropletescaping from the space 11 may be on the surface of the transfer lane 38and might not interfere with a positioning measurement of the grid 32.

FIGS. 25 and 26 refer to the same features as FIGS. 21 and 22 unlessotherwise mentioned. In an embodiment the surface of the grid 32 israised with respect to the surface of the substrate table WT, WT2, asshown in FIG. 25, which corresponds to a cross-section of the substratetable WT, WT2 along the line Y-Y. The surface 60 of the substrate tableWT, WT2 is lower than the surface of the grid plate 32. In the gap 43 inthe grid 32 corresponding to the position of the transfer lane 38, thegrid is raised with respect to the surface of the transfer lane 38, asshown in FIG. 26. FIG. 26 shows a cross-section of the substrate tableWT, WT2 along the line X-X. The surface 60 of the substrate table WT,WT2 is substantially the same height as the transfer lane 38. In thisarrangement a droplet escaping from the space 11 may be on the surfaceof the transfer lane 38 or the surface 60 of the substrate table WT,WT2. Because the surface of the grid 32 is raised the droplet may notreadily contact the surface of the grid plate 32. FIG. 29 shows aperspective view of the embodiment in FIGS. 25 and 26, and shows thegrid 32 is raised with respect to the surface 60 of the substrate tableWT, WT2.

FIG. 30 shows a variation similar to the arrangement in FIG. 29 butwithout the gap 43 in the raised grid 32 for the transfer lane 38. InFIG. 30, the transfer lane 38 passes over the grid 32 which is raisedrelative to the surface 60 of the substrate table WT, WT2. A smoothsurface between the surface of the grid 32 and the lower surface 60 ofthe substrate table WT, WT2 is provided by a ramp 91. Without a step inthe surface between the substrate table WT, WT2 and the grid 32, therisk of liquid loss from the immersion space 11 may be reduced, if notprevented. In an embodiment, a fluid extraction opening 56 may belocated between the surface of the raised grid 32 and the surface 60 ofthe substrate table WT, WT2. The fluid extraction opening 56 may belocated in a recess or groove between the two surfaces 32, 60. Inaddition to having the raised grid, the fluid extraction opening helpsreduce if not prevent liquid in the form of, for example, a droplet fromreaching the surface of the grid 32 from the surface 60 of the tablewithin the grid 32. The fluid extraction opening may serve as a barrierfor liquid which would otherwise flow past it.

FIGS. 27 and 28 refer to the same features as FIGS. 21 and 22 unlessotherwise mentioned. In an embodiment, the grid 32 and the surface 60 ofthe substrate table WT, WT2 are covered with a covering with aprotective surface, for example a transparent plate 62. The transparentplate 62 may be, for example, a fused quartz plate as described in U.S.patent application No. 61/218,712, filed on 19 Jun. 2009, which ishereby incorporated by reference in its entirety. The positioning systemmay operate with the measurements being made through the transparentplate. A droplet does not contact the surface of the grid 32, helpingprevent the grid from becoming contaminated. If the transparent plate 62over the grid becomes contaminated, the plate 62 may cleaned in-situ, orreplaced and optionally cleaned for later re-use.

The surface of the transparent plate 62 may be substantially planar, asshown in FIG. 27 (which corresponds to a cross-section along the lineY-Y in FIG. 20) so that any part of its surface may pass under the fluidhandling structure unrestrictedly. The transparent plate 62 may coverthe portion 44, 46 of the substrate table WT, WT2. Optionally there is agap 43 in the grid 32 corresponding to the location of the transfer lane38. In an embodiment the transparent plate has a ridge 64 at an edge ofthe transfer lane 38. The ridge may be a protrusion from the transparentplate 62 as shown in FIG. 27 which corresponds to a cross-sectionbetween X-X in FIG. 20. The ridge 64 may help limit the movement of adroplet outside the transfer lane 38. The ridge may be part of a barrier50 of the transfer lane 38. An encoder sensor arrangement may be usedlike that shown in FIG. 23 and/or FIG. 24. However, as the plate 62 istransparent to visible radiation it may be transparent to radiation usedby a detector in the positioning system. As the plate 62 may be treated,for example, with a lyophobic (e.g., hydrophobic) coating to repelimmersion liquid, the risk of a droplet or contaminating particle may besufficiently low that the arrangement without a reserve encoder 75 maybe used. In an embodiment the protrusion may be formed from a lyophobic,e.g. hydrophobic, coating. The protrusion 62 is substantially coplanarwith the surface of the transparent plate. The coating may serve thesame function as the protrusion in serving as a barrier to prevent theflow of liquid thereover.

In an embodiment, as shown in FIG. 31 having similar features as FIG.20, between the surrounding surface 60 of the substrate table WT, WT2around the substrate W and the surface of the grid 32 is a barrier 58 inthe form of a lyophobic surface. The lyophobic barrier 58 serves as abarrier to liquid which escapes from the space 11 from reaching thesurface of the grid 32. The lyophobic barrier 58 serves substantiallythe same purpose as the step between the surrounding surface 60 and thesurface of the grid 32 present in the embodiment shown in FIGS. 26, 29and 30. Desirably the lyophobic surface is a two dimensional lyophobicsurface having substantially the same contact angle with respect to theimmersion liquid in two perpendicular directions of movement over thesurface. The barrier 58 extends around the periphery of the surroundingsurface 60, with a gap for passing underneath the immersion space 11during, for example, substrate swap. The gap may correspond to thelocation of the transfer lane 38. The periphery of the barrier 58 maycorrespond to an inner edge of the grid 32.

The same benefit as achieved by lyophobic barrier 58 may be achieved bya barrier in the same location formed by at least one fluid extractionopening or a protrusion 64. In an embodiment the fluid extractionopening is present in a recess or groove in the location of the barrier58. In an embodiment the barrier 58 comprises at one or more selectedfrom: a step in surface height, a protrusion, a contact angle surfaceproperty such as a lyophobic surface, and/or a fluid extraction openingwhich may be located in a recess.

As a droplet may remain on a part of the transfer lane 38, the transferlane may be intermittently cleaned. The cleaning action may be part of aperiodic cleaning cycle, may occur upon detection of a threshold ofcontamination level, or both. Cleaning may be in-situ; it may beautomatic. Such cleaning may be achieved in using a modified fluidhandling structure 12 capable of supplying and removing immersion liquidto clean a surface underneath the fluid handling structure, such as asurface of a table, a removable bridge, a part of a transfer lane 38,and/or a part of a transparent plate 62. Cleaning of at least a part,such as a table or removable bridge, may be off-line (e.g. not part ofthe normal operating procedure). The part may be removed and replaced byanother clean component to reduce downtime. The contaminated part may becleaned for re-use.

FIG. 32 shows an arrangement similar to FIG. 31, except the barrier isan edge barrier 61 located around the periphery, or outer edge, of thegrid 32. The edge barrier 61 helps prevent liquid from flowing off thegrid over the outer edge of the grid 32. Such an arrangement may bedesirable, for example, when cleaning the surface of the grid usingliquid, for example from a liquid confinement structure 12. Liquid lossover the outer edge is reduced, if not prevented. With the barrier 61,less precise control may be required to control the cleaning liquidrelative to the edge of the grid 32. With a reduced need for accuracy,the speed of cleaning of the grid 32 may be increased, so that thecleaning time and downtime for cleaning operations may be reduced andthroughput increased.

During cleaning, liquid may flow towards the surrounding surface 60. Abarrier 58 associated with an inner edge of the grid 32 may be used toreduce, if not prevent, the inward flow of liquid during cleaning. Suchan arrangement is shown in FIG. 33. The barrier 61 does not extend thefull length of the side of the table WT which adjoins the adjoiningtable during substrate swap. On relative movement between the tables WT,WT2, MT and the projection system, the barrier 61 extends so far as toallow a path 93 for a liquid footprint 26 between the tables withoutcrossing the barrier 61. The surface moving under the liquid footprintis substantially continuous, desirably with a consistent contact angle.To clean the surface of the grid 32, the transfer lane 38 may move underthe liquid footprint 26, so that the second table MT, WT2 is under theliquid footprint. The tables MT, WT, WT2 then move so that the grid 32moves under the liquid footprint 26. The movement is in a locusgenerally defined by the outer edge, inner edge or both edges of thegrid (e.g., the path 93) until the substrate table is replaced under theliquid footprint 26 by the second table MT, WT2.

A part of the transfer lane 38 surface may comprise a replaceablecomponent, such as a planar component which may be fixed in place, forexample by adhesive. Such a replaceable component may be a sticker. Asticker may be shaped to cover a specific component, such as a removablebridge 24 and/or a portion 44, 46 of the transfer lane 38. Ifcontamination of a sticker reaches a threshold level, the sticker may becleaned like any other surface. The sticker may be removed and replacedwith a new sticker having the same features and shape as the removedsticker. The sticker may have a specified surface property that maydeteriorate through use, for example by interaction with one or moreselected from: immersion liquid (such as ultra-pure water), exposureradiation and/or contaminating particles (which may derive the substratecoating). Such a surface property may be a lyophobic property, e.g. ahydrophobic property with respect to water, of a certain contact angleor preferred direction, such as a one dimensional lyophobic surface.

An embodiment of transfer lane 38 is an extended surface 63 of a tableWT which extends to contact the side of the second table WT2, MT,covering or overhanging a portion of the second table WT2, MT, as shownin FIGS. 34 and 35. The extended surface may have any of the features ofthe transfer lane herein described, noting that the entire surface ofsuch a transfer lane is a contiguous surface of one substrate table.FIG. 34 shows an arrangement for a substrate table WT with a measurementtable MT. At least one of the tables WT, MT has an extended surface 63.Desirably the measurement table MT has the extended surface becausehaving such a feature on the substrate table may distort the center ofgravity of the table, preventing sufficiently accurate measurement andpositioning of the table and therefore imaging of a substrate on thetable WT.

The part of the grid 32 along the side of the table closest to themeasurement table MT may have a recessed portion. The recessed portionmay correspond to the location of the extended surface 63. The recessedportion may be the entire length of the grid adjoining the measurementtable MT. In use, the surface of the tables that passes under the liquidfootprint 26 includes the extended surface 63. The surface of the grid32 therefore passes the footprint 26, without the grid 32 coming intocontact with the footprint 26 or liquid from the immersion space 11. Therisk of contamination and degradation of the grid 32 is reduced.

FIG. 35 shows an arrangement in a system with two substrate tables. Eachtable WT, WT2 has an extended surface on a similar side. Such anarrangement allows the positions of the two tables to alternate, forexample, for each following substrate swap. The general relativemovement of the footprint 26 and the tables WT, WT2, for example asdepicted, between consecutive substrate swaps is from left to right; therightmost table WT, WT2, moving to the left of the leftmost table forthe following substrate swap Although the following FIGS. 36 to 39 showarrangements which use a measurement table, the described arrangementsmay be modified for use with two substrate tables WT, WT2, each havingan extended surface 63.

FIG. 36 is a cross-section of an embodiment of the arrangement of FIG.34. The extended surface 63 is supported by non-contact support, such asa gas bearing. The gas bearing may form between the undersurface of theextended surface 63 and the facing surface of the substrate table WT,which may be a portion of the grid 32. The gas flow 95 for the gasbearing may be supplied by one or more outlets located in theundersurface of the extended surface 63 and/or in the facing surface ofthe substrate table WT. The gas flow is directed in use towards theother of the undersurface of the extended surface 63 and/or the uppersurface of the facing surface of the substrate table WT. The extendedsurface 63 may be made of thin plate which may be resilient underoperating forces of an immersion system The use of the gas bearing withthe extended surface 63 may improve the stiffness of the extendedsurface 63 without contact between the measurement and substrate tablesMT, WT. Contact between the tables could increase the risk of damage toone or more tables and increase the risk of interference to themeasurement and positioning systems of the tables.

FIG. 37 shows an embodiment where a barrier 68 is formed at a downwardstep 97 between the surrounding surface 60 and the grid 32. The grid 32is lower than the surrounding surface 60, in an embodiment around theperiphery of the substrate table WT, WT2. In an embodiment with the samefeatures, the grid 32 may be located elsewhere, for example on theundersurface of the table. The surface around the periphery of thedownward step 97 may collect immersion liquid which flows onto thesurface. Such liquid may flow off the extended surface. The liquid maybe a droplet which flows down the downward step 97. It may have escapedfrom the immersion liquid in the space 11 during relative motion betweenthe substrate table WT, WT2 and the liquid confinement structure 12.There may be one or more openings in the surface around all or a part ofthe periphery of the downward step 97 to collect, remove or extractliquid from the surface.

FIG. 38 shows a cross-section of the substrate table of FIG. 37 with ameasurement table MT. In an embodiment, to help prevent liquid reachingthe grid 32, the barrier 68 includes a lyophobic surface, a protrusion,and/or at least one fluid extraction opening between the surroundingsurface 60 and the inner edge of the grid 32. In an embodiment, insteadof a gas bearing to help support the extended surface 63, the substratetable has an engagement device 99 such as notch in the substrate tableWT, WT2. During substrate swap a surface of the extended surface 63 maycontact, desirably engage or rest on, the notch 99 as shown in FIG. 39.Such an arrangement avoids the use of gas flows which can have thermallyundesirable effects.

In an aspect, there is provided an immersion lithographic apparatuscomprising: a substrate table configured to support a substrate; a fluidhandling structure configured to supply and confine immersion liquid toa space defined between a projection system and the substrate table, thesubstrate, or both; a swap table configured to be located under thefluid handling structure to retain liquid in the space; and a transfersurface configured to be located under the fluid handling structure andbetween a surface of the substrate table and a surface of the swaptable, wherein the transfer surface is configured to prevent immersionliquid moving over at least part of the transfer surface in a directionwith a component perpendicular to a direction of relative motion betweenthe fluid handling structure and the transfer surface.

In an embodiment, the transfer surface is configured to bridge thesurface of the substrate table and the surface of the swap table, thesurfaces of the substrate table and swap table moveable beneath thefluid handling structure. In an embodiment, between the surfaces of thesubstrate table and the swap table is a positioning surface, apositioning system comprising the positioning surface. In an embodiment,the positioning surface is an encoder grid. In an embodiment, thesubstrate table comprises a transparent plate above the positioningsurface, desirably planar with the transfer surface. In an embodiment,the positioning surface is adjacent the transfer surface. In anembodiment, the positioning surface is raised above the transfersurface. In an embodiment, a protective surface corresponds to theposition of the positioning surface relative to the transfer surface andthe protective surface is above the positioning surface. In anembodiment, the positioning system comprises a plurality of sensorsincluding a sensor to compensate for the transfer surface crossing thepositioning surface. In an embodiment, at least part of the surface ofthe transfer surface is at least part of a surface of the swap table,the substrate table, or both. In an embodiment, facing edges of the swaptable and the substrate table are spaced apart so that between the edgesis a gap. In an embodiment, at least part of the transfer surface ispart of a removable bridge configured to be locatable between the swaptable and the substrate table. In an embodiment, the swap table is: ameasurement table configured not to support a substrate, or a substratetable configured to support a substrate. In an embodiment, the transfersurface is dimensioned to at least exceed the dimension of a liquidfootprint of the fluid handling structure in a plane parallel to thesurface of the transfer surface and perpendicular to the direction ofrelative motion between the fluid handling structure and the transfersurface. In an embodiment, the transfer surface is configured tothermally isolate its surface from the substrate table and desirably theswap table. In an embodiment, the transfer surface comprises a heat pipeconfigured to be operable to compensate a thermal load applied to thetransfer surface. In an embodiment, the surface of the transfer surfaceis lyophobic. In an embodiment, at least part of the transfer surface isprovided by a coating. In an embodiment, the transfer surface comprisesan elongate barrier configured to bar motion of immersion liquid in thedirection with a component perpendicular to the direction of relativemotion between the fluid handling structure and the transfer surface,the barrier being generally aligned in a direction parallel to thedirection of relative motion. In an embodiment, the elongate barriercomprises a surface having increased contact angle relative to anadjacent surface. In an embodiment, the elongate barrier comprises aridge. In an embodiment, the elongate barrier comprises an elongatechannel and an opening in the channel configure to remove fluid from thechannel as the transfer surface moves under the fluid handlingstructure. In an embodiment, the elongate barrier is associated with asharp edge. In an embodiment, the sharp edge is associated with a sideof the transfer surface substantially parallel to the direction ofrelative motion. In an embodiment, the transfer surface comprises atleast a replaceable sticker configured to provide the transfer surface.In an embodiment, the apparatus further comprises the projection system,the projection system configured to direct a patterned beam of radiationtowards a target portion of a substrate. In an embodiment, the swaptable is configured to be located under the fluid handling structureduring swap of the substrate on the substrate table to retain liquid inthe space.

According to an aspect, there is provided a shutter member for animmersion lithographic apparatus, the shutter member having at leastpart of a transfer surface configured to prevent immersion liquid in aconfined space moving over at least part of the transfer surface in adirection with a component perpendicular to a direction of relativemotion between the confined space and the shutter member. In anembodiment, the liquid in the confined space is confined in the space bya fluid handling structure. In an embodiment, the fluid handlingstructure is configured to supply and confine immersion liquid in aspace between a projection system and a facing surface, the facingsurface being the surface of a substrate table configured to support asubstrate, a substrate supported by the substrate table, or a surface ofthe shutter member. In an embodiment, the shutter member is configuredto move under the confined space during substrate swap.

According to an aspect, there is provided a device manufacturing method,the method comprising: confining immersion liquid in a space in contactwith a surface of a substrate table; replacing the surface of thesubstrate table with a shutter surface by moving the substrate table andthe shutter surface in one motion so that the substrate table moves awayfrom under the fluid handling structure and the shutter surface replacesthe surface of the substrate table under the fluid handling structure,wherein in replacing the substrate table with the shutter surface,moving a transfer surface under the fluid handling structure, thetransfer surface preventing immersion liquid moving over at least partof the transfer surface in a direction with a component perpendicular toa direction of motion of the transfer surface. In an embodiment,immersion liquid is supplied to the space and the liquid in the space iscontact with a localized area of the substrate table. In an embodiment,the shutter member comprises a surface of another table.

According to an aspect, there is provided a method of operating animmersion lithographic apparatus, the method comprising: supporting asubstrate on a substrate table; supplying and confining immersion liquidto a space defined by a fluid handling structure between a projectionsystem and the substrate table, the substrate, or both; replacing asurface of the substrate table under the fluid handling structure with ashutter surface, the shutter surface including a surface of a swaptable; moving a transfer surface under the fluid handling structure asthe surface of the swap table replaces the surface of the substratetable; and during moving the transfer surface, preventing immersionliquid moving over at least part of the transfer surface in a directionwith a component perpendicular to a direction of relative motion betweenthe fluid handling structure and the transfer surface.

According to an aspect, there is provided an immersion lithographicapparatus comprising: a substrate table configured to support asubstrate; a fluid handling structure configured to supply and confineimmersion liquid to a space defined between a projection system and thesubstrate table, the substrate, or both; a shutter member configured tobe located under the fluid handling structure during swap of thesubstrate on the substrate table, the shutter member being a swap table,wherein a transfer surface is arranged to be between surfaces of thesubstrate table and the swap table, the transfer surface configured tobe moved under the fluid handling structure and configured to preventimmersion liquid moving over at least part of the transfer surface in adirection with a component perpendicular to a direction of relativemotion between the fluid handling structure and the transfer surface. Inan embodiment, the transfer surface comprises a part of the surface ofthe substrate table, a part of the surface of the swap table, or both.In an embodiment, the apparatus further comprises a bridge locatablebetween the substrate table and the swap table during substrate swap,wherein the transfer surface comprises a top surface of the bridge.

According to an aspect, there is provided an immersion lithographicapparatus, comprising: a substrate table configured to support asubstrate; a fluid handling structure configured to supply and confineimmersion liquid to a space defined between a projection system and thesubstrate table, the substrate, or both; and a transfer surfaceconfigured to be located under the fluid handling structure and betweena surface of the substrate table and a shutter surface, the shuttersurface configured to replace the surface of the substrate table underthe fluid handling structure and the transfer surface configured toprevent immersion liquid moving over at least part of the transfersurface in a direction with a component perpendicular to a direction ofrelative motion between the fluid handling structure and the transfersurface.

Although specific reference may be made in this text to the use oflithographic apparatus in the manufacture of ICs for example an ICdevice, it should be understood that the lithographic apparatusdescribed herein may have other applications, such as the manufacture ofintegrated optical systems, guidance and detection patterns for magneticdomain memories, flat-panel displays, liquid-crystal displays (LCDs),thin-film magnetic heads, etc, such as a device comprising one of theseapplications. The skilled artisan will appreciate that, in the contextof such alternative applications, any use of the terms “wafer” or “die”herein may be considered as synonymous with the more general terms“substrate” or “target portion”, respectively. The substrate referred toherein may be processed, before or after exposure, in for example atrack (a tool that typically applies a layer of resist to a substrateand develops the exposed resist), a metrology tool and/or an inspectiontool. Where applicable, the disclosure herein may be applied to such andother substrate processing tools. Further, the substrate may beprocessed more than once, for example in order to create a multi-layerIC, so that the term substrate used herein may also refer to a substratethat already contains multiple processed layers.

The terms “radiation” and “beam” used herein encompass all types ofelectromagnetic radiation, including ultraviolet (UV) radiation (e.g.having a wavelength of or about 365, 248, 193, 157 or 126 nm). The term“lens”, where the context allows, may refer to any one or combination ofvarious types of optical components, including refractive and reflectiveoptical components.

While specific embodiments of the invention have been described above,it will be appreciated that the invention may be practiced otherwisethan as described. For example, the embodiments of the invention maytake the form of a computer program containing one or more sequences ofmachine-readable instructions describing a method as disclosed above, ora data storage medium (e.g. semiconductor memory, magnetic or opticaldisk) having such a computer program stored therein. Further, themachine readable instruction may be embodied in two or more computerprograms. The two or more computer programs may be stored on one or moredifferent memories and/or data storage media.

The controllers described herein may each or in combination be operablewhen the one or more computer programs are read by one or more computerprocessors located within at least one component of the lithographicapparatus. The controllers may each or in combination have any suitableconfiguration for receiving, processing, and sending signals. One ormore processors are configured to communicate with the at least one ofthe controllers. For example, each controller may include one or moreprocessors for executing the computer programs that includemachine-readable instructions for the methods described above. Thecontrollers may include data storage medium for storing such computerprograms, and/or hardware to receive such medium. So the controller(s)may operate according the machine readable instructions of one or morecomputer programs.

One or more embodiments of the invention may be applied to any immersionlithography apparatus, in particular, but not exclusively, those typesmentioned above and whether the immersion liquid is provided in the formof a bath, only on a localized surface area of the substrate, or isunconfined. In an unconfined arrangement, the immersion liquid may flowover the surface of the substrate and/or substrate table so thatsubstantially the entire uncovered surface of the substrate table and/orsubstrate is wetted. In such an unconfined immersion system, the liquidsupply system may not confine the immersion fluid or it may provide aproportion of immersion liquid confinement, but not substantiallycomplete confinement of the immersion liquid.

A liquid supply system as contemplated herein should be broadlyconstrued. In certain embodiments, it may be a mechanism or combinationof structures that provides a liquid to a space between the projectionsystem and the substrate and/or substrate table. It may comprise acombination of one or more structures, one or more fluid openingsincluding one or more liquid openings, one or more gas openings or oneor more openings for two phase flow. The openings may each be an inletinto the immersion space (or an outlet from a fluid handling structure)or an outlet out of the immersion space (or an inlet into the fluidhandling structure). In an embodiment, a surface of the space may be aportion of the substrate and/or substrate table, or a surface of thespace may completely cover a surface of the substrate and/or substratetable, or the space may envelop the substrate and/or substrate table.The liquid supply system may optionally further include one or moreelements to control the position, quantity, quality, shape, flow rate orany other features of the liquid.

The descriptions above are intended to be illustrative, not limiting.Thus, it will be apparent to one skilled in the art that modificationsmay be made to the invention as described without departing from thescope of the claims set out below.

The invention claimed is:
 1. An immersion lithographic apparatuscomprising: a substrate table configured to support a substrate; a fluidhandling structure configured to supply and confine immersion liquid toa space defined between a projection system and the substrate table, thesubstrate, or both; a swap table configured to be located under thefluid handling structure to retain liquid in the space; and a transfersurface configured to be located under the fluid handling structure andbetween a surface of the substrate table and a surface of the swaptable, wherein the transfer surface is configured to prevent immersionliquid moving over at least part of the transfer surface in a horizontaldirection with a component perpendicular to a direction of relativemotion between the fluid handling structure and the transfer surface. 2.The immersion lithographic apparatus of claim 1, wherein the transfersurface is configured to bridge the surface of the substrate table andthe surface of the swap table, the surfaces of the substrate table andswap table moveable beneath the fluid handling structure.
 3. Theimmersion lithographic apparatus of claim 1, wherein between thesurfaces of the substrate table and the swap table is a positioningsurface, a positioning system comprising the positioning surface.
 4. Theimmersion lithographic apparatus of claim 3, wherein the positioningsurface is an encoder grid.
 5. The immersion lithographic apparatus ofclaim 3, wherein the substrate table comprises a transparent plate abovethe positioning surface.
 6. The immersion lithographic apparatus ofclaim 3, wherein the positioning surface is adjacent the transfersurface.
 7. The immersion lithographic apparatus of claim 3, wherein aprotective surface corresponds to the position of the positioningsurface relative to the transfer surface and the protective surface isabove the positioning surface.
 8. The immersion lithographic apparatusof claim 1, wherein at least part of the surface of the transfer surfaceis at least part of a surface of the swap table, the substrate table, orboth.
 9. The immersion lithographic apparatus of claim 1, wherein thetransfer surface is dimensioned to at least exceed the dimension of aliquid footprint of the fluid handling structure in a plane parallel tothe surface of the transfer surface and perpendicular to the directionof relative motion between the fluid handling structure and the transfersurface.
 10. The immersion lithographic apparatus of claim 1, whereinthe transfer surface is configured to thermally isolate its surface fromthe substrate table.
 11. The immersion lithographic apparatus of claim1, wherein the surface of the transfer surface is lyophobic.
 12. Theimmersion lithographic apparatus of claim 1, wherein the transfersurface comprises an elongate barrier configured to bar motion ofimmersion liquid in the horizontal direction with the componentperpendicular to the direction of relative motion between the fluidhandling structure and the transfer surface, the barrier being generallyaligned in a direction parallel to the direction of relative motion. 13.The immersion lithographic apparatus of claim 12, wherein the elongatebarrier comprises an elongate channel and an opening in the channelconfigure to remove fluid from the channel as the transfer surface movesunder the fluid handling structure.
 14. A shutter member for animmersion lithographic apparatus, the shutter member having at leastpart of a transfer surface configured to prevent immersion liquid in aconfined space moving over at least part of the transfer surface in ahorizontal direction with a component perpendicular to a direction ofrelative motion between the confined space and the shutter member.
 15. Adevice manufacturing method, the method comprising: confining immersionliquid in a space in contact with a surface of a substrate table;replacing the surface of the substrate table with a shutter surface bymoving the substrate table and the shutter surface in one motion so thatthe substrate table moves away from under the fluid handling structureand the shutter surface replaces the surface of the substrate tableunder the fluid handling structure, wherein in replacing the substratetable with the shutter surface, moving a transfer surface under thefluid handling structure, the transfer surface preventing immersionliquid moving over at least part of the transfer surface in a horizontaldirection with a component perpendicular to a direction of motion of thetransfer surface.
 16. A method of operating an immersion lithographicapparatus, the method comprising: supporting a substrate on a substratetable; supplying and confining immersion liquid to a space defined by afluid handling structure between a projection system and the substratetable, the substrate, or both; replacing a surface of the substratetable under the fluid handling structure with a shutter surface, theshutter surface including a surface of a swap table; moving a transfersurface under the fluid handling structure as the surface of the swaptable replaces the surface of the substrate table; and during moving thetransfer surface, the transfer surface preventing immersion liquidmoving over at least part of the transfer surface in a horizontaldirection with a component perpendicular to a direction of relativemotion between the fluid handling structure and the transfer surface.17. An immersion lithographic apparatus comprising: a substrate tableconfigured to support a substrate; a fluid handling structure configuredto supply and confine immersion liquid to a space defined between aprojection system and the substrate table, the substrate, or both; ashutter member configured to be located under the fluid handlingstructure during swap of the substrate on the substrate table, theshutter member being a swap table, wherein a transfer surface isarranged to be between surfaces of the substrate table and the swaptable, the transfer surface configured to be moved under the fluidhandling structure and configured to prevent immersion liquid movingover at least part of the transfer surface in a horizontal directionwith a component perpendicular to a direction of relative motion betweenthe fluid handling structure and the transfer surface.
 18. An immersionlithographic apparatus, comprising: a substrate table configured tosupport a substrate; a fluid handling structure configured to supply andconfine immersion liquid to a space defined between a projection systemand the substrate table, the substrate, or both; and a transfer surfaceconfigured to be located under the fluid handling structure and betweena surface of the substrate table and a shutter surface, the shuttersurface configured to replace the surface of the substrate table underthe fluid handling structure and the transfer surface configured toprevent immersion liquid moving over at least part of the transfersurface in a horizontal direction with a component perpendicular to adirection of relative motion between the fluid handling structure andthe transfer surface.
 19. The immersion lithographic apparatus of claim12, wherein the elongate barrier comprises a surface having increasedcontact angle relative to an adjacent surface.
 20. The immersionlithographic apparatus of claim 12, wherein the elongate barriercomprises a ridge.